The present invention relates generally to underwater breathing devices for supplying air from the surface of a body of water to a diver beneath the surface, and relates more particularly to a self-contained breathing apparatus wherein the surface air is compressed by the diver himself during his underwater activities.
Aside from snorkeling equipment, with which a swimmer is usually limited to a depth of only a few feet below the surface, commercially available underwater breathing equipment falls essentially into two categories: systems wherein air is compressed at the surface and delivered to a diver through a hose; and the self-contained underwater breathing apparatus (scuba) systems characterized by tanks of compressed air which are carried by the diver. The scuba gear permits greater range and freedom of movement than the hose type systems but suffers the disadvantages of limited underwater duration and the encumbering bulk of the tanks. The surface supply systems are expensive and normally require a surface vessel as well as an attendant to monitor the compressor and to pay out or take in the lengthy hose as required by the extent of the diver's underwater travels.
Both of the conventional systems described permit a diver to dive to depths of at least several hundreds of feet with proper training and for such purpose their expense and complexity are tolerable. However, for relatively shallow diving, for example to depths of approximately twenty feet and less, a self-contained breathing apparatus which would utilize the inexhaustable supply of surface air would be more advantageous than either the scuba equipment with its limited duration or the hose type equipment with its surface located compressor.
There have been efforts in the past to develop a self-contained apparatus wherein the cam pressing force is supplied by the diver. For example, U.S. Pat. No. 3,050,055 discloses a system wherein surface air passing through a float-supported air inlet line is compressed by piston-cylinder units mounted on the diver's back and driven by the extension of the diver's legs which serves to extend piston springs which on release compress air drawn into the cylinders. Although such a system might be theoretically feasible, it is handicapped by the fact that the diver's legs must be constantly involved with the air compression function, allowing little time for swimming movement. Furthermore, such a system would be difficult if not impossible to operate while the diver is standing on the bottom or engaged in activities in which movement would not be desirable, such as observing wild life, or working in close quarters with other divers such as in hull inspection or underwater repairing.
A further attempt to free a diver from the limited duration tanks of the Scuba system is shown in U.S. Pat. No. 3,124,131 where air from the surface is drawn into an air reservoir on the diver's back by means of electric motors. While in theory providing a limitless duration of underwater activity, such a system has several drawbacks including a limited range due to the need for an electrical connection to the diver, not to mention the hazard of being wired to an electrical circuit while under water.